Process of the manufacture of nitric acid.



UNITED STATES PATENT o EINAR nnnovn, or NOTODDEN, NORWAY, AISSIGNOR 'ro YNORSK HYDRO-ELEIKTRISK KVAELSTOFAKTIESELSKAB, OF GHRISTIANIA, NORWAY.

rno cnss 0F run MANUFACTURE or NITRIC ACID.

1 ,27 3,991 1V0 Drawing.

may be produced from nitrogen tetroxid,-

water and oxygen by causing the components to react upon one another under pressure in an autoclave. Such a process is described in the German patent specification 225706.

When this process is carried out in the described manner it is however not possible in a reasonable time to obtain a 98%nitric acid, an acid of only about 85% strength being obtained. I have found that it is not possible to obtain an increase in concentration beyond 90% even when the pressure is increased to a very high degree.

According to the present invention a 97% acid may be produced with'a satisfactory output from nitrogen tetroxid, oxygen and water, or from nitrogen tetroxid, oxygenand dilute nitric acid and in a short time of reaction by means of also raising the temperature. The most suitable temperature has been found to be about 70 C. It is known, that chemical reactions proceed at a greater speed at higher temperatures than at lower ones, but in the reaction in question it has however hitherto-been the practice to cantiously avoid the increasing of the temperature, and a cooling has even been made use of during the reaction, it having been assumed that the highest concentration and the highest output were attainable only at a lower temperature, because the dissociation of the nitric acid and the nitrogentetroxid is very low at low temperatures.

As stated, the inventor has found however, that the output as wellas the'concen I tration'of the acid is increased when the tem j Specification of Letters Patent. Patented J 1113 30, 1918:. I I Application man 1a 1918. stratum. 235,410.

perature is raised in spite of the fact that the dissociation of thenitric acid and of the J nitrogen oxid is hereby increased. The d1s--- socation is suitably compensated for by'increasingthe pressure and temperature atthe I same time, so that the working pressure isjf raised beyond the vapor pressure of the nitrogen tetroxid at the reaction tempera,-

ture. A pressure of about 20 atmospheres has been found to be suitable. The reaction is hereby attained in a very short time and at the sametime itis possible to obtain with out difliculties a high percentage nitric acid with a high output calculated upon the nitr'o? 1 1 gen tetroxid employed. In consequence of 5-: the substantial decrease'in the'time of reac tion it is possible to carry out the-process continuously and on an industrial scale. I claim: I

1. A process for the manufacture of highly concentrated nitric acid which comprises causing nitrogen tetroxid, oxygen and Water! to react at a temperature about C. and at a pressure above the vapor pressure of-the tetroxid at the temperature used.

2. A process for the manufacture of highly concentrated nitric acid which comprises causing nitrogen tetroxid, oxygen and dilute nitric acid to react upon one another underpressure of about 20 atmospheres and at a temperature 'ofabout 70 C.

3. A process for the'manufacture 'of highly concentrated nitric acid. which comprises causing nitrogen tetroxid,'oxygen and water to react upon one another under a pressure of about 20 atmospheres and at 'a temperature of about 70 C. o

In testimony that I claim the foregoing as 

